Question

A company xyz has a labelled mass of 500. It has a mean mass of 550 and standard deviation of 20. Assuming that masses are normally destributed at 550 at 5% significance level.

Answer 1

$H_0:\mu=550$ , mean mass is 550 kg

$H_0:\mu\neq550$ , mean mass is not 550 kg

$z=\frac{\overline{x}-\mu}{\sigma}=\frac{500-550}{20}=-2.5$

critical value:

$z_{crit}=1.96$

Since $|z|>z_{crit}$ we reject null hypothesis. Mean mass is not 550 kg